Hydraulic hold-down stripper



5Pt- 24. 1940. R. B. GoRHAM 2,215,643

HYDRAULIC HoLD-nowN STRIPPER Filed March 7, 1959 -jw.. ff

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ATTQRNEY.

Patented Sept. 24, 1940 ics HYDRAULIC HOLD-DOWN STRIPPER Application March 7,

Claims.

This invention relates to hydraulic strippers for punches and the object of they invention is to provide a means for hydraulically operating a punch and for hydraulically stripping the punch 5 after each punching operation.

One of the particular objects of the invention is to strip the metal from the punch after the metal has been punched to prevent the metal from traveling with the punch and this stripping action must be positive to insure that the metal is stripped from the punch subsequently to each operation and prior to the succeeding operation.

Another object of the invention is to provide a stripping mechanism which is hydraulically operated and movable relative to the punch.

Another object of the invention is to provide a stripper which is iirst moved into Contact with the metal to hold it on the die after which the punch is moved through the metal into the die and is drawn back into the stripper to strip the metal from the punch before the stripper is moved away from the metal.

A further object of the invention is. to provide a mechanism for accomplishing these objects hydraulically.

Another object of the invention is to provide a piston whereby the punch may be moved in either direction hydraulically and a stripper operating rod connected to a second piston movable with or in relation to the rst piston to produce the relative motion of the stripper in relation to the punch movement.

These objects and the several novel features of the invention are hereinafter more fully described and claimed and the preferred form of construction by which these objects are attained is shown in the accompanying drawing in which- Fig. 1 is an elevation partly in section ci a punch and stripper constructed in accordance with my invention.

Fig. 2 is a longitudinal section through the punch and stripper taken on line 2--2 of Fig. 1 showing the same in the down position.

Fig, 3 is a transverse section thro-ugh the device taken on line 3 3 of Fig. 1.

Fig. 4 is a section sho-wing the stripper and punch in the up position.

The device comprises a body member I having bolt holes 2 whereby the device may be attached to a vertical support. This body I is provided with a member 3 reciprocable longitudinally therein and a packing li is provided about the member 3 to prevent leakage of the hydraulic medium. The member 3 at the upper end is secured to a piston 5 which is reciprocable in a cylinder 6 and this cylinder t is secured between the body member l and the head l by the bolts 8 shown in Figs. l and 2. The packing l is held in place by a member 9 which is threaded into the body I after the packing has been positioned 1939, Serial No. 260,368

above the member 3 and at the lower end of the member 3 is a member i0 which is secured to the member 3 by the screw I E shown in Figs. 1 and 2. This member ID is cylindricalin form and ts within a cylindrical bore in the' body l. ing plate I2 is provided at the lower end of the member l and a punch holder i3 is secured to the backing plate i2 and the member I6 by the screws I4. A punch l5 issecured in the member i3 and the lower end thereof is arranged to fit into a die I5 which is held in a die block I'l secured to the extending portion i8 of the body I and this extending portion i8 is provided with an aperture i9 through which the punched out pieces may fall.

A pressure conduit 2G is connected to the body I and leads through a channel 2l to an annular chamber 22 about the member 3 so that when the hydraulic medium under pressure passes through the pressure conduit 2Q and into the chamber 22 it will raise the piston 5 in the cylinder 6 to lift the punch I5 out of the die I6. At the upper end of its stroke this piston engages the head l. For the downward or punching movement, a conduit 23 is connected to the head 'l and the hydraulic medium may flow thro-ugh this conduit 23 and through the conduit 2li in the head into the cylindrical chamber 25 to move the piston 5 downwardly. This piston 5 moves the member 3 downwardly and the member it which is attached thereto and also moves the punch i5 into the die l. Consequently, by directing the hydraulic 4medium under pressure through the conduits 20 and 23 the punch may be raised or lowered as desired.

The stripper comprises a member 26 having an opening 2l therein about the punch and this stripper is provided with a pair of side arms 28 attached thereto by the screws 29 sho-wn in Figs. 1 and 3. At the upper ends, these arms 28 are attached to a cross bar Sil by the screws 3l and this cross bar extends through slots provided therefor in the body l and members I6 and 3 as will be understood from Figs. 1, 2 and 3. Also7 the arms 28 ride in ways 32 provided therefor in opposite sides. of the body I as will be understood from Fig. 3. The slot for the cross bar 3i] is of 'greater depth than the bar as will be understood from ,Figs 1 and 2 leaving a space 33 in which the cross bar 3Q `is movable in relation to the members I0 and 3.

Upward movementof the bar 3 is provided by the rod or plunger 35 whichengages the bar 3U as shown in Figs. l and 2. This rod 35 eX- tends through the member 3 and at the upper end is provided with a piston 3S thereon tting the cylinder 3l in the head l. In order to allow flow of hydraulic medium into the cylinder 3i', a conduit 38 is provided connecting the conduit 39 which leads into the cylinder 31. This conduit A backv 38 is normally closed by a spring pressed ball 40 which is held against its seat by a light spring 4| so that as the conduit 23 and cylinder 25 are filled with the hydraulic medium under pressure from the pressure conduit 23 the hydraulic medium under pressure will unseat the ball 40 and allow the hydraulic mediumto pass through the conduits 38 and 39 to lill the cylindrical chamber 37. Thus, when oil enters the conduit 24 under pressure, it fills the cylindrical chambers 31 and 25 thus applying pressure to the pistons and 36 to move the same downwardly simultaneously, the piston 36 moving slightly faster than the piston 5 and causing the stripper 26 to engage the metal being punched just before or at about the time the punch engages the metal. The stripper and bar 30 are thus stopped against movement and the punch continues to move by reason of continued movement of the piston 5. As the flow of the hydraulic medium is reversed and caused to iiow through the pressure conduit 2U, it will move the piston 5 upwardly thus raising the punch out of the die but, due to the fact that the hydraulic medium is. trapped in the chamber 31 while the hydraulic medium in the chamber 25 has a free outlet through the conduit 24, the upward movement of the stripper is prevented until the pressure in the chamber 3'! becomes sufficient to overcome the stiff spring 44 which holds the check valve 42 in position to close the aperture 43.

This spring is preferably of suicient stiffness so that the valve 42 is not opened until the bar 30 is picked up by the members forming the bottom of the slot 33 as the punch is moving upwardly. As this bar is picked up by upward movement of the punch and members 3 and l0, the pressure in the chamber 3l becomes sufficient to unseat the ball check 42 and allow the hydraulic medium from the chamber 31 to pass into the conduit 24 which at that time is acting as the outlet conduit. By this arrangement after the punching operation the punch is rst withdrawn from the die and up into the stripper and as the pressure is maintained on the stripper to hold it against the work by the hydraulic pressure in the chamber 3l the metal is held while the punch is withdrawn from the metal and after the punch has been withdrawn suiiiciently to allow the bottom of the slot 33 to engage the bar 30 the stripper is then carried up with the punch but the punch at that time has receded into the stripper. Also, it is to be noted that on the downward movement the punch end is receded within the stripper so that the stripper first engages the metal to be punched. The punch is then forced through the metal and drawn back through the metal into the stripper before the pressure of the stripper on the work is released.

From the foregoing description it becomes evident that the device is very simple and efficient in operation, will automatically strip the metal from the punch after each punching operation, will maintain a pressure on the metal during the punching operation and provides a device whic accomplishes the objects described. v

Having thus fully described my invention, its utility and mode of operation, what I claim and desire to secure by Letters Patent of the United States is l. In a stripper for hydraulically operated punches, fa body,a membermovable longitudinally in either direction therein, a punch secured to the lower end of said member, a piston secured to the upper end thereof, hydraulically operated means for moving the piston longitudinally in either direction, a stripper tting about the punch and having a cross bar extending through member, the slot in said member for the cross bar being of greater depth than the crossv bar whereby upon movement of the piston in one direction the cross bar and stripper are lifted as the end of the Slot engages the cross bar, a second piston having a stem engaging the cross bar, means for moving the pistons in one direction together and means yieldably resisting movement of the second piston in the opposite direction by the cross bar.

2. A hydraulic stripper for punches comprising a piston for moving the punch longitudinally in either direction, a stripper slidable in relation to the punch, a second piston having a stem movable through the first piston and engaging the stripper, hydraulic means for moving the first piston in either direction, hydraulic means for moving the second piston in one direction, means carried by the rst piston for moving the second piston on movement of the first piston in one direction and hydraulic means resisting Said movement of the second piston.

3. A hydraulic stripper for punches comprising a piston for moving the punch longitudinally in either direction, a stripper slidable in relation to the punch, a second piston having a stem movable through the first piston and engaging the stripper, hydraulic means for moving both pistons in one direction, means for moving the second piston by movement of the first piston in one direction and means preventing movement of the second piston until the iirst piston has traveled through a portion of its stroke.

4. In a hydraulic stripper for hydraulically operated punches, a piston movable longitudinally in either directionl by a hydraulic medium under pressure, a punch secured' to move with said piston, a second piston movable in one direction by a hydraulic medium under pressure, a stripper connected to move with the second piston and means for moving the second piston in the opposite direction by movement of the first piston, said means being limited to a predetermined extent so that the stripper' is moved after the punch has begun its movement.

5. A hydraulic stripper for punches comprising a piston connected to the punch and movable longitudinally in either direction by hydraulic pressure, a stripper fitting about the punch and movable longitudinally in relation to the punch, a second piston, a stem on the second piston movable through the first piston and engaging the stripper, the arrangement being such that upon movement ofthe first piston in relation to the second piston the punch is moved in relation to the stripper.

6. In a stripper for hydraulically operated punches in which the punch is raised and lowered by hydraulic pressure, a stripper through which the punch is operated, hydraulically operated means for moving the stripper in one direction ahead of the punch and means connected with the punch for moving the stripper by movement of the punch in the opposite direction, said means operating after the punch has started its movement.

RALPH B. GORI-IAM. 

